The molecular characterization of human and experimental renal injury has resulted in two consistent insights. First the intrinsic population of kidney cells are not passive bystanders injured by infiltrating leukocytes. Rather resident cells become "activated" after injury and participate in the subsequent destructive and restorative processes that ensue. Second renal cells serve as a source and target of biological modifiers that mediate nephron injury and repair. Third extracellular matrix composition is modified. How these observation collaborate to induce tissue injury is not understood but definition of more proximate regulators of these events is necessary to effectively interrupt the pathogenic mechanisms that drive nephron destruction. Our laboratory has focused on the IL-1 activated mesangial cell in an effort to define molecular and cellular mechanisms of progressive renal disease. Our published and preliminary data demonstrate: 1) IL-1 induces specialized changes in MC structure and function inpart by induction of a specific gene set; 2) MC cultured under standard conditions express an "activated" or inflammatory phenotype but when appropriately cultured retain a more in vivo-like phenotype; 3) proinflammatory mediators and matrix remodelling collaborate to transcriptionally activate an inflammatory MC phenotype. From these data, we hypothesize that a ECM-dependent change in cell shape is permissive for cytokine mediated changes in cell structure and function. This project fits into the broad experimental goals of our laboratory to molecularly define mechanisms of the cytokine-activated phenotype in vitro and to assess whether such a "defined' MC phenotype can be identified in vivo. We will test our hypothesis using three model systems; MC cultured on plastic; MC cultured on various substratum; and in an animal model of primary mesangial injury. We will specifically: 1. Define further the transmembrane signalling pathways activate by the IL-1-IL-1R interaction in MC cultured on plastic. a. What kinases are activated: We will asses for change in phosphorylation state by immunoprecipitation and subsequent immunoblotting. b. What proteins interact with the IL-1 receptor. Expression library screening and yeast genetics. II. Determine how change i cell substratum interactions affect cell biology by assessing effects of proinflammatory mediators and matrix on a- smooth muscle expression as a model gene. a. stress vs integrins b. 5'-regulatory regions III. To analyze changes in ECM gene expression and indicators of mesangial cell activation in a model of primary mesangial injury. a. immunohistochemistry, in situ etc b. to change intraglomerular gene expression by in vivo gene transfer